1. Field of the Invention
The invention relates to a buzzer, more particularly to a piezoelectric buzzer.
2. Description of the Related Art
As shown in FIGS. 1 and 2, a conventional piezoelectric buzzer 1 includes a first housing 11, a second housing 12 coupled to the first housing 11 and cooperating with the first housing 11 to define a resonant chamber 10, a buzzer unit 13 disposed in the resonant chamber 10, and conductive first and second terminals 14, 15.
The second housing 12 includes a base plate 121 and a pair of spaced apart insert seats 122, each of which protrudes outwardly from the base plate 121 and is formed with an insert hole 123. The buzzer unit 13 includes a metallic vibrating plate 131, and a piezoelectric plate 132 made from ceramic material and attached to the vibrating plate 131.
Each of the first and second terminals 14, 15 is inserted into the insert hole 123 in a respective one of the insert seats 122 of the second housing 12. The first terminal 14 has a first connection section 141 extending outwardly of the resonant chamber 10, a first extending section 142 extending from the first connection section 141 into the resonant chamber 10 and extending toward the buzzer unit 13, and a first contact point 143 spot-welded to one end of the first extending section 142 and contacting electrically the vibrating plate 131 of the buzzer unit 13. The second terminal 15 has a second connection section 151 extending outwardly of the resonant chamber 10, a second extending section 152 extending from the second connection section 151 into the resonant chamber 10 and extending toward the buzzer unit 13, and a second contact point 153 spot-welded to one end of the second extending section 152 and contacting electrically the piezoelectric plate 132 of the buzzer unit 13. Application of an alternating current voltage to the vibrating plate 131 and the piezoelectric plate 132 via the first and second connection sections 141, 151 will cause mechanical distortion of the vibrating plate 131 due to the piezoelectric effect, thereby generating sounds.
To firmly position the first and second terminals 14, 15, the insert seats 122 of the second housing 12 are disposed to protrude outwardly from the base plate 121 of the second housing 12 for making the insert holes 123 deeper. However, the outwardly protruding insert seats 122 result in a relatively thick piezoelectric buzzer. The thickness of the conventional piezoelectric buzzer is 6.8 millimeters measured from the first housing 11 to the base plate 121 of the second housing 12, which hinders application to some electronic devices, such as on-board units (OBU) for Electronic Toll Collection (ETC) system (the maximum standard thickness being 6.2 millimeters). Moreover, the relatively large distances between each of the first and second connection sections 141, 151 and the buzzer unit 3 weaken the resilient contact forces of the first and second extending sections 142, 152 for abutting respectively against the vibrating plate 131 and the piezoelectric plate 132, thereby resulting in poor contact quality therebetween. Furthermore, the spot-welding of the first and second contact points 143, 153 results in a relatively complicated and time-consuming manufacturing process for the piezoelectric buzzer.